09/02/1991
Area code 510 was put into service. Area code 510 was created from a split of area code 415. In 1998 area code 510 was split to form area code 925.

Counties in California within area code 510 include:

Alameda County, and Contra Costa County.

Major cities or places in California within area code 510 include:

Area code 510 serves much of the Eastern Bay area in Alameda County and the western portion of Contra Costa County in California including the larger cities and communities of Alameda, Berkeley, Castro Valley, El Cerrito, Fremont, Hayward, Newark, Oakland, Richmond, San Leandro, San Lorenzo, San Pablo, and Union City in addition to many smaller communities.